Degradation of a tetramethylarsonium salt by microorganisms occurring in sediments and suspended substances under both aerobic and anaerobic conditions

Microbial degradation of a tetramethylarsonium salt during incubation at 25°C was investigated under both aerobic and anaerobic conditions. Two media (1/5 ZoBell 2216E and inorganic salt medium), added with the sediments or suspended substances as the sources of the microorganisms, were used. Degradation of the tetramethylarsonium salt occurred only in the ZoBell medium: under anaerobic conditions, trimethylarsine oxide and dimethylarsinic acid were derived with the sediments, and dimethylarsinic acid with the suspended substances, the salt degrading more rapidly with the former than with the latter. Small amounts of two metabolites, trimethylarsine oxide and inorganic arsenic(V), was also derived in the aerobically incubated ZoBell medium added with the suspended substances. This result means that the tetramethylarsonium salt is degraded to inorganic arsenic, which is the starting material for arsenic circulation in marine ecosystems, via trimethylarsine oxide and dimethylarsinic acid.     

Synthesis of adamantane derivatives—43: 1,3-Dipolar cycloaddition reactivity of methyleneadamantane derivatives with substituted benzonitrile oxides

The 1,3-dipolar cycloaddition reactivity and regioselectivity of methyleneadamantane 1, ethyl adamantylideneacetate 7a, adamantylideneacetonitrile 7b and ω-methoxymethyleneadamantane 7c with substituted benzonitrile oxides 3a-i were calculated by CNDO/2 method using the perturbation equation derived by Klopman and Salem. The calculation predicted an exclusive formation of adamantan - 2 - spiro - 5' - 3' - aryl - Δ²' - isooxazoline 4a-i in the reactions of 1, 7a and 7b with 3a-i, and a formation of 67–69:33-31 mixture of 4a-i and isomeric 5a-i in the reaction of 7c with 3a-i. The predicted exclusive formation of 4a-i were experimentally observed in the reactions of 1,7a and 7b with 3a-i generated from 2a-i with Et₃N or thermally, but the reaction of 7c with 3a did not afford the corresponding adducts. A considerably higher reactivity of CN triple bond than CC double bond was observed in the reaction of 7b with 3a and 1,2,4-oxadiazole derivative 11 was obtained as the major product.     

Ubiquity of arsenobetaine in marine animals and degradation of arsenobetaine by sedimentary micro-organisms

Arsenic compounds were extracted with chloroform/methanol/water from tissues of marine animals (four carnivores, five herbivores, five plankton feeders). The extracts were purified by cation and anion exchange chromatography. Arsenobetaine [(CH₃)₃As⁺CH₂COO^?], dimethylarsinic acid [(CH₃)₂AsOOH], trimethylarsine oxide [(CH₃)₃AsO] and arsenite, arsenate, and methylarsonic acid [(CH₃)AsO(OH)₂] as a group with the same retention time were identified by high-pressure liquid chromatography. Arsenic was determined in the collected fractions by graphite furnace atomic absorption spectrometry. Arsenobetaine found in all the animals was almost always the most abundant arsenic compound in the extracts. These results show that arsenobetaine is present in marine animals independently of their feeding habits and trophic levels. Arsenobetaine-containing growth media (ZoBell 2216E; solution of inorganic salts) were mixed with coastal marine sediments as the source of microorganisms. Arsenobetaine was converted in both media to trimethylarsine oxide and trimethylarsine oxide was converted to arsenite, arsenate or methylarsonic acid but not to dimethylarsinic acid. The conversion rates in the inorganic medium were faster than in the ZoBell medium. Two dominant bacterial strains isolated from the inorganic medium and identified as members of the Vibro–Aeromonas group were incapable of degrading arsenobetaine.     

Synergic liquid/liquid extraction of lithium and sodium with 4-acyl-5-pyrazolones with bulky substituents and tri-n-octylphosphine oxide

The synergic liquid/liquid extraction of lithium and sodium with 4-acyl-5-pyrazolones having bulky substituents and tri-n-octylphosphine oxide (TOPO) is described. The maximum percentage extraction and the separation of lithium and sodium were improved by introducing bulky substituents. Quantitative extraction (? 99% ) of lithium could be achieved by adduct formation with TOPO, which enhanced the extraction much more than did triphenylphosphine oxide. The extraction decreased in the solvent order cyclohexane ? benzene ? chloroform, which is the general trend in synergic extractions.     

Positron lifetimes and distributions in the infinite-layer compound SrCuO2 and related materials

We have calculated distributions and lifetimes of positrons in the infinite-layer compound SrCuO₂ and those trapped at possible point defects therein. In the delocalized state, positrons show their density maxima at interstitial sites in the Sr planes and have a significant overlap also with Cu and O atoms. The corresponding positron lifetime is 149 ps. It has been revealed that the Sr vacancy strongly localizes positrons with the binding energy of 2.8 eV and the lifetime of 238 ps, while the O vacancy does not trap positrons. Calculations are also performed on related materials Sr₂Cu₄O₆ and Sr₄Cu₆O₁₀, which are characterized by one-dimensional networks of edge-sharing CuO₄ squares. Positrons are predominantly distributed between these networks in these materials and their corresponding lifetimes are 170–171 ps.     

Proton and Li-7 NMR study on the effect of the OH− anion upon the Li+-ion conduction in the solid solution Li5NI2LiOH

From ¹H and ⁷LiNMR relaxation times T₁, T₂ and T_1ρ in Li₅NI₂ and the solid solution Li₅NI₂?0.77LiOH, the diffusive motion of the Li⁺ ion was studied to make clear the role of the OH^? ion in improving the Li⁺ ionic conduction. At temperatures as low as 140 K, each Li⁺ ion jumps among four available positions. Its activation energies are 9.26 and 11.8 kJ mol^?1 for Li₅NI₂ and Li₅NI₂?0.77LiOH, respectively. Diffusive motion was observed in T₂ and T_1ρ above 240 K. The mode of the cation distribution and the diffusion mechanism are not affected by the presence of the OH^? anion. The most noticeable fact is that the OH^? ion is substituted selectively for the N^3? ion that is the nearest neighbour of the Li⁺ ion. This selective substitution increases the concentration of the Li⁺ vacancy most effectively up to 4.2% of the total Li positions. At the same time it diminishes the strong attractive force of the N^3? anion binding the Li⁺ ion to the position, and thus the activation energy. For the diffusion, an anomalously low attempt frequency of 3̃ × 10⁹Hz was obtained from T_1ρ, while the normal value of 4.8 × 10¹²Hz was obtained from the ionic conductivity. The large discrepancy was attributed to the collective nature of the Li⁺ diffusive motion.     

Sequential-injection on-line preconcentration using chitosan resin functionalized with 2-amino-5-hydroxy benzoic acid for the determination of trace elements in environmental water samples by inductively coupled plasma-atomic emission spectrometry

A new chelating resin using chitosan as a base material was synthesized. Functional moiety of 2-amino-5-hydroxy benzoic acid (AHBA) was chemically bonded to the amino group of cross-linked chitosan (CCTS) through the arm of chloromethyloxirane (CCTS-AHBA resin). Several elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and rare earth elements (REEs), could be adsorbed on the resin. To use the resin for on-line pretreatment, the resin was packed in a mini-column and installed into a sequential-injection/automated pretreatment system (Auto-Pret System) coupled with inductively coupled plasma-atomic emission spectrometry (ICP-AES). The sequential-injection/automated pretreatment system was a laboratory-assembled, and the program was written using Visual Basic software. This system can provide easy operation procedures, less reagent consumption, as well as less waste production.

Experimental variables considered as effective factors in the improvement sensitivity, such as an eluent concentration, a sample and an eluent flow rate, pH of samples, and air-sandwiched eluent were carefully optimized. The proposed system provides excellent on-line collection efficiency, as well as high concentration factors of analytes in water samples, which results in highly sensitive detection of ultra-trace and trace analysis. Under the optimal conditions, the detection limits of 24 elements examined are in the range from ppt to sub-ppb levels. The proposed method was validated by using the standard reference material of a river water, SLRS-4, and the applicability was further demonstrated to the on-line collection/concentration of trace elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and REEs in water samples.     

First systematic band-filling control in organic conductors

The systematic study of band-filling control for four kinds of organic conductors with various kinds of ground states has succeeded. (1) By partial substitution of (GaCl(4))(-) by (MCl(4))(2-) [M = Co, Zn] in the anion blocking layer of lambda-ET(2)(GaCl(4))(-) [ET = bis(ethylenedithio)tetrathiafulvalene], single crystals of lambda-ET(2)(GaCl(4))(-)(1-x)(MCl(4))(2-)(x) [x = 0.0, 0.05, 0.06] have been obtained. The resistivity at room temperature decreases from 3 Omega cm (x = 0.0) to 0.1 Omega cm (x = 0.06) by doping to the antiferromagnet with an effective half-filled band (x = 0.0). (2) Another 2:1 (donor/anion) salt, delta'-ET(2)(GaCl(4))(-), which is a spin gap material, has been doped as delta'-ET(2)(GaCl(4))(-)(1-x)(MCl(4))(2-)(x) [x = 0.05, 0.14]. The resistivity is lowered from 10 Omega cm (x = 0.0) to 0.3 Omega cm (x = 0.14). For both 2:1 salts, the semiconducting behaviors have transferred to relatively conductive semiconducting ones by doping. (3) As for alpha-type 3:1 salts, the parent material is in a charge-ordering state such as alpha-(ET(+)ET(+)ET(0))(CoCl(4))(2-)(TCE), where the charge-ordered donors are dispersed in the two-dimensional conducting layer. Although the calculation of alpha-ET(3)(CoCl(4))(2-)(TCE) shows a band-insulating nature, and the crystal structure analysis indicates that this material is in a charge-ordering state, the metallic behavior down to 165 K has been observed. With doping of (GaCl(4))(-) to the alpha-system, isostructural alpha-ET(3)(CoCl(4))(2-)(1-x)(GaCl(4))(-)(x)(TCE) [x = 0.54, 0.57, 0.62] have been afforded, where the pattern of the horizontal stripe-type charge ordering changes with an increase of x. (4) By doping (GaCl(4))(-) to the 3:2 gapless band insulator which is isostructural to beta'-ET(3)(MCl(4))(2)(2-) [M = Zn, Mn], the obtained beta'-ET(3)(CoCl(4))(2-)(2-x)(GaCl(4))(-)(x) [x = 0.66, 0.88] shows metallic behavior down to 100 and 140 K, respectively. They are the first metallic states in organic conductors by band-filling control of the gapless band insulator. These systematic studies of band-filling control suggest that the doping to the gapless band insulator with a pseudo-1/2-filled band is most effective.